The Moss LNG carrier with spherical aluminium tanks has, through a service period of almost 30 years, built up an almost unparalleled record regarding safety, reliability and availability. All the vessels of this type ever built were still in service when this was written. Several vessels have already been certified for an extended operating period of 20 years. No doubt a life span of 40 to 50 years will be the rule rather than the exception for this containment system.

The authors believe that the most important reason for this success is the integrity and robustness inherent in the spherical shell design. Nevertheless, the design and construction methods of the spherical shell/skirt concept have over the years been refined by the licensed building yards and by Moss Maritime as the proprietary owner. At regular intervals, the concept has been re-examined with respect to new design tools and construction methods as part of a continuous quest for enhanced safety and overall cost efficiency. A number of tank shapes and tank/hull configurations based on the single containment shell have been examined and evaluated. Recently, efforts have also been made in other areas, such as reliquefaction of boil-off, diesel propulsion, manoeuvrability and general vessel refinement.

This work has been undertaken in extensive co-operation with the shipyards that are building LNG carriers with Moss spherical tanks. The authors also feel that it is important to utilise the potential of the continuous developments in data technology for the next generation of LNG carriers. In this paper we will therefore outline the possibilities and advantages of fully integrated systems as proposed by one of the principal players in this field (Kongsberg Simrad).

By incorporating the positive results of recent development work into the standard 137k carrier hull frame, the result is a more cost effective LNG carrier. The improvements are in our opinion of such significance that we feel justified in presenting it to the LNG industry as A New Generation Moss LNG Carrier. The concept retains the proven overall safety and robustness of the single barrier spherical containment system and we believe that the significant reduction in transportation cost which this concept represents, will be of interest to owners and operators of LNG carriers

Paper Delivered by:
Per Christiansen
Lars Sannes
Masanori Mizuno

Prepared for:
Gastech Houston 2000

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